1. Field of Invention
The present invention relates to an improved system for counting and stacking sheets of paper or signatures and would normally be used in conjunction with a printing process. In the printing process, a continuous sheet or web of paper is processed by first passing it through the printing process; second, passing it through an oven to dry the web and remove solvents and ink resins; third, passing the web through a folding and cutting system to transform the printed web into a series of shingled or overlapping individual sheets; and, finally, conveying the shingled sheets into a counting and stacking system to count and stack the sheets into stacks of a predetermined number of sheets.
It is desirable to provide a counting and stacking system in which the counting means controls the operation of the stacker and which stacker also provides an improved means for separating and stacking preselected quantities of sheets in such a way as to avoid jamming the system. Previous stacking systems which did not employ any type of counting means would normally be controlled or operated by the delivery or folding system which feeds into the stacker. Under such an arrangement, however, the stacker would continue operating as long as the delivery or folding system was operating. With the present invention, the stacker can be actuated by the sheet counting means which can shut down the stacker when the flow of sheets is completed. Operation in this manner avoids the necessity of employing labor to solely operate the stacking system.
The prior art discloses various types of devices for stacking sheets. Particularly, these prior devices make use of wedges or other insertion means to separate the continuous flow of sheets into distinct stacks by inserting the wedge in the direction opposite sheet flow. See, U.S. Pat. Nos. 3,566,757 and 3,568,578. The inherent problem in separating sheets in a direction opposite sheet flow is that such a method of separation creates a high probability of lead edge fouling or inaccurate segregation of sheets.
Other prior art devices separate sheets from beneath and in the same direction of sheet flow. However, these devices employ more than one insertion means. See, U.S. Pat. No. 2,853,299, U.S. Pat. No. 4,359,218 and U.S. Pat. No. 4,111,411. The present invention overcomes the problems and limitations associated with these prior devices and improves upon the prior art stackers by achieving separation and stacking of the sheets through the use of a single insertion device from beneath and in the direction of sheet flow.
The preferred embodiment of the present invention also employs an optical counting system to count the sheets. A transmitter emits a beam of light which, when interrupted, causes a counter to register a counted unit. Optical counters have been previously used to count sheets as seen in U.S. Pat. No. 3,834,289. However, the present invention improves upon previous optical counting arrangements. In U.S. Pat. No. 3,834,289, for example, the feed conveyor is angled and is required to be elevated above the conveyor discharging the sheets from the counter. The present invention alleviates all of the common problems associated with angled and duel level conveyors by using a level conveyor system while still achieving accurate counting.